Rock wool for insulated bricks

Clay Technology magazine
1 Apr 2008
Unipor's Coriso bricks are filled with thermal insulating rock wool

An insulating brick filled with rock wool has been developed by German company Unipor, a conglomerate of brick manufacturers headquartered in Munich, and ceramic building materials equipment producer Lingl, based in Krumbach. The product is said to have better thermal insulation properties than other bricks filled with materials such as polystyrene or perlite.

The Coriso brick is based on Unipor’s W, WS and S ranges of bricks, which contain 35 rows of perforated holes. ‘That is more or less the most holes we can put in a brick [to improve air convection and insulation],’ explains Dr Thomas Fehlhaber, CEO of Unipor. ‘The only way to improve it further is to fill the holes with an insulation that is better than the air on the inside.’

The company decided to use granules of rock containing no inorganic compounds. Engineers were inspired by mineral wool produced by Rockwool, based in Hedehusene, Denmark, who spin molten lava into fibres six to 10µm in diameter. These fibres prevent the movement of air, making them excellent thermal insulators. However, the granules are too large to fit into the holes of the Unipor bricks.

‘We needed to improve the process and build a factory to make the granules, which we did last year,’ says Fehlhaber. Unipor’s patented brick filling unit was installed by Lingl at a brickworks in Puttenhausen in October 2007, and today there are three more plants in Germany producing the specialised product.

Mixing water with basalt, Unipor designers heat the mixture to over 1,000ºC until it reaches a molten state, after which it is spun on a wheel to create a woollen structure. It is then injected into the brick’s holes.

To insert soft wool into the Coriso bricks, Unipor had to design an entirely new filling device. ‘The machine fills them in like snow falling into the brick,’ explains Fehlhaber.

This adds extra time to the production process, and can be expensive – an extra
euro per brick, bringing the entire brick price up to four euros. But, according to Fehlhaber, while other high-thermal insulation bricks have a thermal conductivity of 0.1 lambda (measured in watts per meter per degrees Kelvin), the filled Coriso has a lambda of 0.08 – an improvement of 20%.

The company does not currently offer the Coriso bricks to foreign customers, but hopes to soon. ‘A year ago no one had even heard of Coriso. We need to get settled in the German market before we go abroad,’ says Fehlhaber.


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